1. Field of the Invention
The present invention relates to fluorescent glass, an optical waveguide including the fluorescent glass, an optical fiber including the fluorescent glass, an optical coherence tomography apparatus including the optical waveguide, and an optical fiber laser including the optical fiber.
2. Related Background Art
Fluorescent glass doped with a laser active material generates ASE (Amplified Spontaneous Emission) by amplifying spontaneous emission (fluorescence) occurring when the laser active material pumped with pumping light returns to its ground state, or amplifies signal light by a phenomenon of stimulated emission. Examples of the laser active material added to the fluorescent glass include transition metals such as Bi, Cr, and Ni and rare-earth elements such as Er, Yb, Tm, and Nd.
The fluorescent glass generates fluorescence in a wider band when doped with a transition metal than when doped with a rare-earth element. Therefore, applying the fluorescent glass doped with transition metals to optical amplifiers which can collectively amplify a wide band of light and light sources has been under consideration. Such applied technologies are described, for example, in Documents 1 to 6 in the following:
Document 1: Japanese Patent Application Laid-Open No. 2002-252397
Document 2: Japanese Patent Application Laid-Open No. 2003-283028
Document 3: U.S. Patent Application Laid-Open No. 2003/0063892
Document 4: T. Suzuki et al., CLEO 2004, Tech. Dig., CtuD6, 2004
Document 5: C. Batchelor et al., Applied Physics Letters, Vol. 82, No. 23, pp. 4035-4037, 2003
Document 6: M. Peng et al., Optics Letters, Vol. 29, No. 17, pp. 1998-2000, 2004
The above-mentioned Documents 1, 2, and 6 describe fluorescent glass products doped with Bi. On the other hand, the above-mentioned Documents 3 to 5 disclose fluorescent glass products doped with Cr or Ni.